Microfluidics involves micro-scale devices that handle small volumes of fluids, e.g., microliter, nanoliter, picoliter, or femtoliter volumes. Because microfluidic devices can accurately and reproducibly control and dispense small fluid volumes, in particular volumes less than 1 μl, they have the potential to provide significant cost-savings. The use of microfluidics technology reduces cycle times, shortens time-to-results, and increase throughput. Furthermore incorporation of microfluidics technology enhances system integration and automation.
Liquid bridge technology involves sample droplet formation utilizing immiscible fluids and is useful in microfluidic devices. Sample droplets are formed at an end of an inlet port that extends into a chamber that is filled with a carrier fluid. The carrier fluid is immiscible with the sample droplet. The sample droplet grows until large enough to span a gap to an outlet port in the chamber, forming an axisymmetric liquid bridge. By adjusting the flow rate or by introducing a second sample droplet to the first sample droplet, an unstable funicular bridge is formed that subsequently ruptures from the inlet port. After rupturing from the inlet port, the sample droplet enters the outlet port, surrounded by the carrier fluid from the chamber. The process then repeats itself.
Given the small dimensions of microfluidic systems that utilize liquid bridge technology, introduction of gas into the system can present significant operational problems. Gas can be introduction into a liquid bridge system is during sample acquisition, i.e., interaction between a sample tip and a vessel for acquiring the sample and introducing the sample into the system. Once gas is introduced into the system, the system should be shutdown and purged to remove the gas. Purging the system and re-equilibrating the system for operation wastes time and valuable resources.
There is an unmet need for devices and systems that can acquire a sample and interface with a system without introducing a gas into the system.